ISO/IEC 15416:2016

INTERNATIONAL ISO/IEC
STANDARD 15416
Second edition
2016-12-15
Automatic identification and data
capture techniques — Bar code print
quality test specification — Linear
symbols
Techniques automatiques d’identification et de capture des
données — Spécifications pour essai de qualité d’impression des codes
à barres — Symboles linéaires
Reference number
©
ISO/IEC 2016
© ISO/IEC 2016, Published in Switzerland
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ii © ISO/IEC 2016 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 2
4.1 Abbreviated terms . 2
4.2 Symbols . 3
5 Measurement methodology . 4
5.1 General requirements . 4
5.2 Reference reflectivity measurements . 4
5.2.1 General. 4
5.2.2 Measurement light source . 4
5.2.3 Measuring aperture . 4
5.2.4 Optical geometry . 5
5.2.5 Inspection band . 6
5.2.6 Number of scans . 7
5.3 Scan reflectance profile . 7
5.4 Scan reflectance profile assessment parameters . 8
5.4.1 General. 8
5.4.2 Element determination . 9
5.4.3 Edge determination . 9
5.4.4 Decode .10
5.4.5 Symbol contrast (SC) .10
5.4.6 Edge contrast (EC) .10
5.4.7 Modulation (MOD) .10
5.4.8 Defects .10
5.4.9 Decodability .12
5.4.10 Quiet zone check .13
6 Symbol grading .13
6.1 General .13
6.2 Scan reflectance profile grading .13
6.2.1 Decode .14
6.2.2 Reflectance parameter grading .14
6.2.3 Decodability .14
6.3 Expression of symbol grade .15
7 Substrate characteristics .15
Annex A (normative) Decodability .16
Annex B (informative) Example of symbol quality grading .17
Annex C (informative) Substrate characteristics .19
Annex D (informative) Interpretation of the scan reflectance profile and profile grades .23
Annex E (informative) Guidance on selection of light wavelength .26
Annex F (informative) Guidance on number of scans per symbol .28
Annex G (informative) Example of verification report .29
Annex H (informative) Comparison with traditional methodologies .30
Annex I (informative) Process control requirements .33
Bibliography .36
© ISO/IEC 2016 – All rights reserved iii

Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are
members of ISO or IEC participate in the development of International Standards through technical
committees established by the respective organization to deal with particular fields of technical
activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other international
organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the
work. In the field of information technology, ISO and IEC have established a joint technical committee,
ISO/IEC JTC 1.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for
the different types of document should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject
of patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent
rights. Details of any patent rights identified during the development of the document will be in the
Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/IEC JTC 1, Information technology, Subcommittee
SC 31, Automatic identification and data capture techniques.
This second edition cancels and replaces the first edition (ISO/IEC 15416:2000), which has been
technically revised with the following changes, as well as minor editorial modifications:
— the computation of “Defects” was modified in this revision of ISO/IEC 15416 (see Note 3 in 5.4.8); and
— sharp boundaries between grade levels are avoided by assigning grades within grade boundaries to
the first decimal place (see the Notes in 6.2.2 and 6.2.3).
iv © ISO/IEC 2016 – All rights reserved

Introduction
The technology of bar coding is based on the recognition of patterns encoded in bars and spaces of
defined dimensions according to rules defining the translation of characters into such patterns, known
as the symbology specification.
The bar code symbol is produced in such a way as to be reliably decoded at the point of use, if it is to
fulfil its basic objective as a machine readable data carrier.
Manufacturers of bar code equipment and the producers and users of bar code symbols therefore
require publicly available standard test specifications for the objective assessment of the quality of
bar code symbols, to which they can refer to when developing equipment and application standards or
determining the quality of the symbols. Such test specifications form the basis for the development of
measuring equipment for process control and quality assurance purposes during symbol production,
as well as afterwards.
The performance of measuring equipment is the subject of a separate standard, ISO/IEC 15426-1.
This document is to be read in conjunction with the symbology specification applicable to the bar code
symbol being tested, which provides symbology-specific detail necessary for its application.
This methodology provides symbol producers and their trading partners a universally standardized
means for communicating about the quality of bar code symbols after they have been printed.
© ISO/IEC 2016 – All rights reserved v

INTERNATIONAL STANDARD ISO/IEC 15416:2016(E)
Automatic identification and data capture techniques —
Bar code print quality test specification — Linear symbols
1 Scope
This document:
— specifies the methodology for the measurement of specific attributes of bar code symbols;
— defines a method for evaluating these measurements and deriving an overall assessment of symbol
quality; and
— provides information on possible causes of deviation from optimum grades to assist users in taking
appropriate corrective action.
This document applies to those symbologies for which a reference decode algorithm has been defined,
and which are intended to be read using linear scanning methods, but its methodology can be applied
partially or wholly to other symbologies.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC 19762 and the
following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
3.1
bar reflectance
lowest reflectance value in the scan reflectance profile of a bar element
3.2
decode
determination of the information encoded in a bar code symbol
3.3
edge contrast
difference between bar reflectance (3.1) and space reflectance (3.14) of two adjacent elements
3.4
element reflectance non-uniformity
reflectance difference between the highest peak (3.9) and the lowest valley (3.16) in the scan reflectance
profile of an individual element or quiet zone
3.5
global threshold
reflectance level midway between the maximum and minimum reflectance values in a scan reflectance
profile used for the initial identification of elements
© ISO/IEC 2016 – All rights reserved 1

3.6
inspection band
band (usually from 10 % to 90 % of the height of a bar code symbol) across which measurements are taken
Note 1 to entry: See Figure 2.
3.7
measuring aperture
opening which governs the effective sample area (3.10) of the symbol, and the dimensions of which at
1:1 magnification is equal to that of the sample area
3.8
modulation
ratio of minimum edge contrast (3.3) to symbol contrast (3.15)
3.9
peak
point of higher reflectance in a scan reflectance profile with points of lower reflectance on either side
3.10
sample area
effective area of the symbol within the field of view of the measurement device
3.11
scan path
line along which the centre of the sample area (3.10) traverses the symbol, including quiet zones
3.12
show-through
property of a substrate that allows underlying markings or materials to affect the reflectance of the
substrate
3.13
space
light element corresponding to a region of a scan reflectance profile above the global threshold (3.5)
3.14
space reflectance
highest reflectance value in the scan reflectance profile of a space element or quiet zone
3.15
symbol contrast
difference between the maximum and minimum reflectance values in a scan reflectance profile
3.16
valley
point of lower reflectance in a scan reflectance profile with points of higher reflectance on either side
4 Symbols and abbreviated terms
4.1 Abbreviated terms
EC edge contrast
EC minimum value of EC
min
ERN element reflectance non-uniformity
ERN maximum value of ERN
max
2 © ISO/IEC 2016 – All rights reserved

GT global threshold
MOD modulation
PCS print contrast signal
RT reference threshold
SC symbol contrast
4.2 Symbols
A average achieved width of element or element combinations of a particular type
c defect adjustment constant
e width of widest narrow element
E width of narrowest wide element
e i’th edge to similar edge measurement, counting from leading edge of symbol character
i
F factor used to soften the effect on defect grades derived from small changes peaks and valleys
within an element
K smallest absolute difference between a measurement and a reference threshold
k number of element pairs in a symbol character in a (n, k) symbology
M width of element showing greatest deviation from A
m number of modules in a symbol character
N average achieved wide to narrow ratio
n number of modules in a symbol character in a (n, k) symbology
R bar reflectance
b
R dark reflectance
D
R light reflectance
L
R maximum reflectance
max
R minimum reflectance
min
R space reflectance
s
RT reference threshold between measurements j and (j + 1) modules wide
j
S total width of a character
V decodability value
V decodability value for a symbol character
C
Z average achieved narrow element dimension or module size, as measured
© ISO/IEC 2016 – All rights reserved 3

5 Measurement methodology
5.1 General requirements
The measurement methodology defined in this document is designed to maximize the consistency of
both reflectivity and bar and space width measurements of bar code symbols on various substrates.
This methodology is also intended to correlate with conditions encountered in bar code scanning
hardware.
Measurements shall be made with a defined light source (such as a single light wavelength) and a
measuring aperture of dimensions defined by the application specification or determined in accordance
with 5.2.1 and 5.2.2. A circular aperture is defined by its diameter in accordance with Table 1.
Application specifications may define other aperture diameters or shapes.
Whenever possible, measurements shall be made on the bar code symbol in its final configuration, i.e.
the configuration in which it is intended to be scanned. If this is impossible, refer to Annex C for the
method to be used for measuring reflectance for non-opaque substrates.
The sampling method should be based on a statistically valid sample size within the lot or batch being
tested. A minimum grade for acceptability shall be established prior to quality control inspection. In the
absence of a sampling plan defined in formal quality assurance procedures or by bilateral agreement, a
suitable plan may be based on the recommendations in ISO 2859-1.
5.2 Reference reflectivity measurements
5.2.1 General
Equipment for assessing the quality of bar code symbols in accordance with this document shall
comprise a means of measuring and analysing the variations in the diffuse reflectivity of a bar code
symbol on its substrate along a number of scan paths which shall traverse the full width of the symbol
including both quiet zones. The basis of this methodology is the measurement of diffuse reflectance
from the symbol.
All measurements on a bar code symbol shall be made within the inspection band defined in accordance
with 5.2.4.
The measured reflectance values shall be expressed in percentage terms by means of calibration
and reference to recognized national standards laboratories, where 100 % should correspond to the
reflectance of a barium sulphate or magnesium oxide reference sample.
5.2.2 Measurement light source
The light source used for measurements should be specified in the application specification to suit the
intended scanning environment. When the light source is not specified in the application specification,
measurements should be made using the light source that approximates most closely to the light source
expected to be used in the scanning process. Light sources may include narrow band or broad band
illumination. Refer to Annex E for guidance on the selection of the light source.
5.2.3 Measuring aperture
The nominal diameter of the measuring aperture should be specified by the user application
specification to suit the intended scanning environment. When the measuring aperture diameter
is not specified in the application specification, Table 1 should be used as a guide. In an application
where a range of X dimensions will be encountered, all measurements shall be made with the aperture
appropriate to the smallest X dimension to be encountered.
In the absence of a defined X dimension, the Z dimension shall be substituted.
4 © ISO/IEC 2016 – All rights reserved

The effective measuring aperture diameter may vary slightly from its nominal dimension due to
manufacturing tolerances and optical effects. Note that the measured width of some of the narrow
elements may be smaller than the measuring aperture diameter.
Table 1 — Guideline for diameter of measuring aperture
X Dimension Aperture diameter Reference
(mm) (mm) number
0,100 ≤ X < 0,180 0,075 03
0,180 ≤ X < 0,330 0,125 05
0,330 ≤ X < 0,635 0,250 10
0,635 < X 0,500 20
NOTE The aperture reference number approximates to the measuring aperture diameter in
thousandths of an inch.
NOTE The measuring aperture is not to be confused with the F-number of a lens.
5.2.4 Optical geometry
The reference optical geometry for reflectivity measurements shall consist of the following:
a) a source of incident illumination which is uniform across the sample area at 45° from a perpendicular
to the surface, and in a plane containing the illumination source that shall be both perpendicular to
the surface and parallel to the bars;
b) a light collection device, the axis of which is perpendicular to the surface.
The light reflected from a circular sample area of the surface shall be collected within a cone; the angle
at the vertex of which is 15°, centred on the perpendicular to the surface, through a circular measuring
aperture, the diameter of which at 1:1 magnification shall be equivalent to that of the sample area.
NOTE Figure 1 illustrates the principle of the optical arrangement, but is not intended to represent an
actual device.
This reference geometry is intended to minimize the effects of specular reflection and to maximize
those of diffuse reflection from the symbol. It is intended to provide a reference basis to assist the
consistency of measurement. It may not correspond with the optical geometry of individual scanning
systems. Alternative optical geometries and components may be used, provided that their performance
can be correlated with that of the reference optical arrangement defined in this subclause.
© ISO/IEC 2016 – All rights reserved 5

Key
1 light sensing element
2 aperture at 1:1 magnification (measurement A = measurement B)
3 baffle
4 sample
5 light source
Figure 1 — Reference optical arrangement
5.2.5 Inspection band
The area within which all measurement scan paths shall lie shall be contained between two lines
perpendicular to the height of the bars of the symbol, as illustrated in Figure 2. The lower line shall
be positioned at a distance above the average lower edge of the bar pattern of the symbol while the
upper line shall be positioned at the same distance below the average upper edge of the bar pattern of
the symbol. This distance shall be equal to 10 % of the average bar height or the measuring aperture
diameter, whichever is greater. The inspection band shall extend to the full width of the symbol
including quiet zones.
6 © ISO/IEC 2016 – All rights reserved

Key
1 inspection band (normally 80 % of average bar height)
2 10 % of average bar height, or aperture diameter if greater, above inspection band
3 10 % of average bar height, or aperture diameter if greater, above average bar bottom edge
4 quiet zones
5 scanning lines
6 average bar bottom edge
Figure 2 — Inspection band
5.2.6 Number of scans
In order to provide for the effects of variations in symbol characteristics at different positions in the
height of the bars, a number of scans shall be performed across the full width of the symbol including
both quiet zones with the appropriate measuring aperture and a light source of defined nominal
wavelength. These scans shall be approximately equally spaced through the height of the inspection
band. The minimum number of scans per symbol should normally be 10 or the height of the inspection
band divided by the measuring aperture diameter, whichever is lower. Refer to Annex F for guidance on
the number of scans.
The overall quality grade of the symbol is determined by averaging the quality grades of the individual
scans, in accordance with Clause 6.
5.3 Scan reflectance profile
Bar code symbol quality assessment shall be based on an analysis of the scan reflectance profiles. The
scan reflectance profile is a plot of reflectance against linear distance across the symbol. If scanning
speed is not constant, measuring devices plotting reflectance against time should make provision
to compensate for the effects of acceleration or deceleration. If the plot is not a continuous analogue
profile, the measurement intervals should be sufficiently small to ensure that no significant detail is
lost and that dimensional accuracy is adequate.
Figure 3 is a graphical representation of a scan reflectance profile. The vertical axis represents
reflectance and the horizontal axis linear position. The high-reflectance areas are spaces and the
low-reflectance areas are bars. The high-reflectance areas on the extreme left and right are the quiet
zones. The important features of the scan reflectance profile can be determined by manual graphical
© ISO/IEC 2016 – All rights reserved 7

analysis or automatically by numerical analysis. For example, the highest reflectance point on the scan
reflectance profile in Figure 3 is approximately 82 % and the lowest is approximately 10 %.
Figure 3 — Scan reflectance profile
5.4 Scan reflectance profile assessment parameters
5.4.1 General
The scan reflectance profile parameters described in 5.4.2 to 5.4.9 shall be assessed for compliance
with this document. Grading of the scan reflectance profile parameters is described in 6.2. Figure 4 is
the same scan reflectance profile as Figure 3 with certain features indicated.
8 © ISO/IEC 2016 – All rights reserved

Figure 4 — Features of scan reflectance profile
5.4.2 Element determination
To locate the bars and spaces, a global threshold shall be established. The global threshold shall be
the reflectance value midway between the highest and lowest reflectance values measured in the scan
reflectance profile, or:
GT = (R + R )/2
max min
where
R is the highest reflectance value;
max
R is the lowest reflectance value.
min
Each region above the global threshold shall be regarded as a space and the highest reflectance value
in the region shall be designated the space reflectance, R . Similarly, the region below the global
s
threshold shall be regarded as a bar and the lowest reflectance in the region shall be designated the bar
reflectance, R .
b
For each space, R − GT represents its reflectance margin above the global threshold. For each bar,
s
GT − R represents its reflectance margin below the global threshold. A warning should be issued
b
when the minimum reflectance margin for any element is less than 5 % of the SC of a symbol. This
warning should caution users to consider the possibility that this symbol is close to an F grade for edge
determination.
NOTE This warning is not required and this recommendation is newly introduced in this revision of this
document.
5.4.3 Edge determination
An element edge shall be defined as being located at the point where the scan reflectance profile
intersects the mid-point between R and R of two adjacent regions, i.e. where the reflectance value is
s b
(R + R )/2. If more than one point satisfying this definition exists between adjoining elements, then
s b
© ISO/IEC 2016 – All rights reserved 9

the edge position and the element widths will be ambiguous and the scan reflectance profile shall fail
the decode parameter. The quiet zones and intercharacter gaps, if any, are considered to be spaces.
5.4.4 Decode
The symbology reference decode algorithm shall be used to decode the symbol using the element edges
determined in 5.4.3. This algorithm may be found in the symbology specification.
5.4.5 Symbol contrast (SC)
Symbol contrast is the difference between the highest and lowest reflectance values in a scan
reflectance profile.
SC = R − R
max min
5.4.6 Edge contrast (EC)
Edge contrast is the difference between the R and R of adjoining elements including quiet zones. The
s b
lowest value of edge contrast found in the scan reflectance profile is the minimum edge contrast, EC .
min
EC = R − R
s b
5.4.7 Modulation (MOD)
Modulation is the ratio of the minimum edge contrast to symbol contrast.
MOD = EC /SC
min
5.4.8 Defects
Defects are irregularities found within elements and quiet zones, and are measured in terms of element
reflectance non-uniformity.
Element reflectance non-uniformity within an individual element or quiet zone is the difference
between the reflectance of the highest peak and the reflectance of the lowest valley. When an element
consists of a single peak or valley, its reflectance non-uniformity is zero. The highest value of element
reflectance non-uniformity found in the scan reflectance profile is the maximum element reflectance
non-uniformity. Defect measurement is expressed as the ratio of the maximum element reflectance
non-uniformity (ERN ) to symbol contrast.
max
a) Define the defect adjustment constant “c” equal to 0,075.
NOTE 1 “c” corresponds to the following:
—   a small amount of “noise” to be reduced to eliminate instability in measurement;
—   an amount of contrast difference that is small enough for scanners to ignore.
NOTE 2 If “c” would be defined as 0, the method described here is equivalent to the defect grade specified
in the previous edition of this document in all cases (because the factor, F, defined below, would always be
equal to 1).
b) For each bar element.
1) For each positive Peak Maxima in the element:
i) find the lowest valley to the left of it within the element, called R ;
minLeft
ii) find the lowest valley to the right of it within the element, called R ;
minRight
iii) calculate ERN as the Peak Maximum − R ;
left minLeft
10 © ISO/IEC 2016 – All rights reserved

iv) calculate ERN as the Peak Maximum − R ;
right minRight
v) take the lesser of ERN and ERN as ERN′ (ERN prime);
left right
vi) set F to the value 1 if ERN′ ≥ c. If ERN′ < c, then calculate F = ERN′/c;
vii) calculate the provisional ERN for this peak (and only this peak) as F × MAX (ERN ,
left
ERN ).
right
2) Take the maximum of the provisional ERN values from all iterations of the previous step as the
ERN of this element.
c) Same as b) for each space element, and as follows.
1) For each negative Valley Minima (a local minima):
i) find the highest peak to the left of it within the element, called R ;
maxLeft
ii) find the highest peak to the right of it within the element, called R ;
maxRight
iii) calculate ERN as R − the Valley minimum;
left maxLeft
iv) calculate ERN as R − the Valley minimum;
right maxRight
v) take the lesser of ERN and ERN as ERN′ (ERN prime);
left right
vi) set F to the value 1 if ERN′ ≥ c. If ERN′ < c, then calculate F = ERN′/c;
vii) calculate the provisional for this valley (and only this valley) as F × MAX (ERN , ERN ).
left right
2) Take the maximum of all the provisional ERN values from all iterations of the previous step as
the ERN of this element.
d) Take the maximum of all ERN values from b) 2) and c) 2) as ERN for the overall scan.
max
Defects = ERN /SC
max
NOTE 3 The calculation of ERN described above is modified in this revision of this document.
max
Three cases are especially useful to illustrate the functioning of this algorithm. The leftmost example
shown in Figure 5 is an example of a case that will be affected by this change. The defect will be reduced
because ERN is very small (in particular, it is much less than “c”). The middle example shows a case
left
where many peaks and valleys exist within an element, but ERN and ERN are much larger than
left right
“c”. The defect measurement will not be affected by this change. The rightmost example is actually
equivalent to the middle example in as much as this algorithm is concerned, even though ERN and
left
ERN are different for each local maxima.
right
Figure 5 — Examples to illustrate ERN calculation
© ISO/IEC 2016 – All rights reserved 11

5.4.9 Decodability
The decodability of a bar code symbol is a measure of the accuracy of its production in relation to the
appropriate reference decode algorithm. Bar code scanning equipment can generally be expected to
perform better on symbols with higher levels of decodability than on those with lower decodability.
Rules governing the nominal dimensions for each bar code symbology are given in particular symbology
specifications. The reference decode algorithm allows reasonable margin for errors in the printing and
reading processes by defining one or more reference thresholds at which a decision is made as to the
widths of elements or other measurements.
The decodability of a scan reflectance profile is the fraction of available margin which has not been
consumed by the printing process and is thus available for the scanning process. When calculating the
decodability value, V, for a scan reflectance profile, regard shall be to the measurements required by
the reference decode algorithm in the relevant symbology specification. In the following paragraph, the
term “measurement” shall be taken to refer to either to a single element width, in symbologies which
use these directly in the reference decode algorithm (e.g. “Code 39”), or to the combined width of two
or more adjacent elements, in symbologies using edge to similar edge measurements for decoding (e.g.
“Code 128”).
The decodability value is calculated with reference to the following:
a) the average achieved width (referred to in the formula below as A) for measurements of a particular
type [e.g. narrow elements, or bar + space combinations nominally totalling 2 (or 3, or 4 .) modules]
in the scan reflectance profile;
b) the reference threshold applicable to measurements of the same type as A (referred to in the
formula below as RT);
c) the actual measurement showing the greatest deviation from A in the direction of the reference
threshold, (referred to in the formula below as M).
The general form of the formula for calculating V is as follows:
V = absolute value of [(RT − M)/(RT − A)]
where
(RT − M) is the remaining margin not used by printing variation;
(RT − A) is the total theoretical margin based on the ideal measurement of the element(s).
Figure 6 illustrates this principle. The shaded area represents the range of measurements of the same
type as A (e.g. narrow elements). All measurements are taken from 0.
Figure 6 — Principle of decodability measurement
12 © ISO/IEC 2016 – All rights reserved

More specific formulae applicable to either two-width symbologies or (n, k) symbologies are defined in
Annex A. Reference should also be made to the symbology specification for the particular computation
of decodability unique to each symbology.
5.4.10 Quiet zone check
The average narrow element width, Z, shall be calculated and revised quiet zones determined based
on this dimension. R , ERN of the quiet zones and R of the quiet zones, as used in the initial scan
max s
reflectance profile analysis, shall be compared with new values obtained for the revised quiet zones. If
the value(s) differ, then affected portions of the scan reflectance profile analysis shall be repeated.
6 Symbol grading
6.1 General
As a consequence of the use of different types of bar code reading equipment under differing conditions
in actual applications, the level of quality required of a bar code symbol to ensure an acceptable level of
performance will differ. Application specifications should therefore define the required performance in
terms of symbol grade in accordance with this document, following the guidelines in D.3.
Symbol grading shall be used to derive a relative measure of symbol quality under the measurement
conditions used. Each scan reflectance profile shall be analysed and assigned a grade on a descending
scale from 4 to 0 in steps of 0,1. The grade 4 represents the highest quality, while the grade 0 represents
failure. The scan reflectance profile grade for each scan reflectance profile shall be the lowest grade of
any parameter in that scan reflectance profile. The overall symbol grade shall be the arithmetic mean
of the scan reflectance profile grades. If any two scans of the same symbol yield different decoded data,
then the overall symbol grade, irrespective of individual scan reflectance profile grades, shall be 0. An
example of a symbol quality grading is given in Annex B. For the interpretation of the scan reflectance
profile and profile grades, see Annex D.
In order to determine the causes of poor quality grades, it is necessary to examine the grades for each
parameter in the scan reflectance profile in question as described in D.2. For process control purposes,
the averages of the grade for each parameter obtained from all the scan reflectance profiles may
provide meaningful guidance (see I.4). If the grades alone do not provide sufficient explanation, it may
also be necessary to examine the plot(s) of the scan reflectance profile(s).
6.2 Scan reflectance profile grading
The scan reflectance profile grade shall be the lowest grade of the following:
a) decode;
b) symbol contrast (SC);
c) minimum reflectance (R );
min
d) minimum edge contrast (EC );
min
e) modulation (MOD);
f) defects;
g) decodability (V);
h) any additional requirements imposed by the application or symbology specification.
It is appropriate to measure these parameters in the sequence given above.
© ISO/IEC 2016 – All rights reserved 13

6.2.1 Decode
Decodable symbols shall comply with the symbology specification, notably in respect of character
encodation, start and stop patterns, symbol check character(s), quiet zones and intercharacter gaps
(where applicable). If the scan reflectance profile cannot be decoded using the symbology reference
decode algorithm, then it shall receive the failing grade 0. Otherwise, it shall receive the grade 4.
6.2.2 Reflectance parameter grading
Depending on their values, symbol contrast, modulation and defects may be graded from 4,0 to 0 in
steps of 0,1; minimum reflectance and minimum edge contrast grades may be graded either 4 or 0.
These parameters are interdependent and need to be considered together.
Table 2 defines the parameter values corresponding to the various grades.
Table 2 — Reflectance parameter grading
Grade R SC EC MOD Defects
min min
4,0 ≤0,5 R ≥70 % ≥15 % ≥0,70 ≤0,15
max
3,0 ≥55 % ≥0,60 ≤0,20
2,0 ≥40 % ≥0,50 ≤0,25
1,0 ≥20 % ≥0,40 ≤0,30
0 >0,5 R <20 % <15 % <0,40 >0,30
max
For SC, MOD and defects, the grade shall be computed as an interpolated value, rounded to the nearest
0,1 in between grade levels. For example, SC of 52 % shall result in a grade of 2,8 and MOD of 0,69 shall
results in a grade of 3,9. In the lowest range, the grade shall be interpolated from 1 down to 0, except
defect which shall be 0 for all values greater than 0,30. The decimal part of the SC grade is computed as
the fraction of the range for the grade of 2 (15 %) that the measured value (52 %) exceeds the minimum
value for a grade of 2 (40 %), computed as 2 + [(52 % − 40 %)/15 %].
NOTE The interpolation described above is a new feature in this revision of this document and is introduced
as a way of reducing meaningless grade level fluctuations when small changes in measurements cause a grade to
transition between grade levels.
6.2.3 Decodability
The decodability value, V, for each scan reflectance profile shall be calculated according to the formula
for the type of symbology in question set out in Annex A, supplemented where necessary by formulae
specific to the symbology in question, contained in the symbology specification. Decodability is graded
from 4 to 0, rounded to the nearest 0,1, in between grade levels according to Table 3. For example, for V
of 0,56 shall result in a grade of 3,5 and V of 0,20 shall result in a grade of 0,8.
Table 3 — Decodability grades
V Grade
≥0,62 4
≥0,50 3
≥0,37 2
≥0,25 1
a
<0,25 0
a
For values less than 0,25, interpolate from 1 down to 0.
NOTE The interpolation described above is a new feature in this revision of this document and is introduced
as a way of reducing meaningless grade level fluctuations when small changes in measurements cause a grade to
transition between grade levels.
14 © ISO/IEC 2016 – All rights reserved

6.3 Expression of symbol grade
A symbol grade is only meaningful if it is expressed in conjunction with the measurement light source
and aperture used. It should be shown in the format G/A/L, where G is the overall symbol grade, i.e. the
arithmetic mean of the scan reflectance profile grades to one decimal place, A is the aperture reference
number, from Table 1, and L indicates the light source, by the light peak wavelength in nanometres
for narrow band illumination, the letter “W” for white (broad band) illumination, or other designator
defined by an application specification.
For example, 2,7/05/660 would indicate that the average of the grades of the scan reflectance profiles
was 2,7 when these scan reflectance profiles were obtained with the use of a 0,125 mm aperture (ref.
no. 05) and a 660 nm light source.
7 Substrate characteristics
Certain characteristics of the substrate, notably gloss, low opacity and the presence of an over-laminate
may affect reflectance measurements, and the recommendations in Annex C should be taken into
account if any of these factors
...